No Vegeta just shot a blast that detonated it. Doesn't mean it had the same power. And they never slap away planet destroying blasts. The blasts that are said to have the power to destroy the planet were either shot up into the sky or blocked by another attack. And Superman has survived a lot stronger things that a planet destroying blast. A sun exploding after being hit multiple times with red sun energy, beams of kryptonite, and magical blasts that can destroy islands, and while encases in kryptonite laced sand nuked himself and wasn't even harmed. Sure blasts like that may seem weak compared to the ultimate blasts of DBZ that are said to destroy planets but they're his weakness also or while he was weakened. And they're a lot stronger than any blasts than most blasts that are actually used.